Polar molecules can be manipulated using strong electric fields.
Many techniques have been developed for the manipulation of small
molecules in low-field-seeking quantum states. However, application
of these techniques to large molecules is not straightforward,
because, for larger molecules, all states are high-field seeking at
the relevant electric field strengths.

In order to spatially focus molecules in high-field seeking states
alternating gradient (dynamic) focusing has to be applied [1]. This
method has been succesfully used, for instance, for the alternating
gradient deceleration of benzonitrile [2] and for the conformer
selection of 3-aminophenol in an m/µ-selector [3].

Here we discuss how the resolution of such a selector can be
optimized by changing the duty cycle of the AC switching sequence
and present corresponding experimental results. Furthermore,
simulations for a second generation m/µ-selector employing an
improved mechanical setup and higher electric fields will be
presented.